CLINICAL CONTEXT

No one feels good about a high-stress, low-reward job, but can high-strain jobs actually kill you? Kivimäki and colleagues evaluated this issue in a long-term prospective cohort study that was published in the October 19, 2002, issue of the BMJ. [1] The researchers observed 812 workers for a mean of 25.6 years, with the purpose of understanding how their employment affected rates of cardiovascular mortality. All participants were free of cardiovascular disease at baseline.

Participants with high-strain jobs, which were defined according to a high level of demands at work with a low level of control, experienced a hazard ratio (HR) for cardiovascular mortality of 2.2 (95% confidence interval [CI], 1.2-4.2) compared with workers with low job strain. This result was not significantly changed after adjustment to account for biological and behavioral risk factors at baseline.
Effort-reward imbalance, as defined by low salary, lack of social approval, and few opportunities for career advancement, was associated with a HR for cardiovascular mortality of 2.4 (95% CI, 1.3-4.4). However, the component of poor job control alone was not associated with a significant increase in the risk for cardiovascular mortality.

Despite these findings, job strain has only inconsistently been linked with a higher risk for stroke specifically. The current study by Dingli Xu and colleagues uses a meta-analysis to better understand the relationship between job strain and stroke.

STUDY SYNOPSIS AND PERSPECTIVE

Working in a highly stressful job may raise the risk for stroke, particularly for women, suggests a meta-analysis of relevant research.

“Epidemiological studies have shown that high strain jobs are associated with an increased risk of coronary heart disease. However, studies regarding the association between job strain categories and the risk of stroke are inconsistent,” investigator Dingli Xu, MD, from Southern Medical University in Guangzhou, China, told Medscape Medical News.

“In this meta-analysis, we included data from more than 130,000 individuals and found that being exposed to high-strain jobs was associated with an increased risk of stroke, especially for ischemic stroke. The harmful effect of work stress may be more significant in women,” Dr Xu said.

The analysis, which was published online October 14 in Neurology,[2] included 6 studies on job strain and stroke risk involving a total of 138,782 participants who were followed up for 3 to 17 years.

Jobs were classified into 1 of 4 categories according to how much control workers had over their jobs and how hard they worked, or the psychological (but not physical) demands of the job, such as time pressure, mental load, and coordination burdens. They are:

Passive jobs with low demand and low control, including the jobs performed by janitors, miners, and other manual laborers.

Low-strain jobs with low demand and high control, such as those done by natural scientists and architects.

High-strain jobs with high demand and low control, as found in service industry workers (waitresses and nursing aides, for example). This category made up 11% to 27% of participants in all 6 studies.

Active jobs with high demand and high control, including those performed by physicians, teachers, and engineers.

The researchers found that people with high-strain jobs had a 22% higher risk for stroke than those with low-strain jobs (relative risk [RR], 1.22; 95% CI, 1.01-1.47). The risk with high-strain work was most pronounced for ischemic stroke (RR, 1.58; 95% CI, 1.12-2.23) and in women (RR, 1.33; 95% CI, 1.04-1.69). No other job strain types were associated with stroke risk.

The researchers calculated a population-attributable risk for stroke with high-strain jobs of 4.4% overall and 6.5% for women.

“Many mechanisms may be involved in the association between high-stress job and the risk for stroke,” said Dr Xu. “The most important is that high-stress jobs may lead to more unhealthy behaviors, such as poor eating habits, smoking, and a lack of exercise. So it is of vital importance for subjects with high-stress occupations to address these lifestyle issues.”

“Second, psychotherapy methods aiming to help [the] individual to cope with psychological stress, such as cognitive-behavioral therapy, relaxation therapy, and multimodal interventions, may be needed in high-risk subpopulations with high- strain occupations combined with other cardiovascular risk factors, especially in women,” Dr Xu added.

The fact that job stress was measured at only one point and that other factors, such as high blood pressure or high cholesterol levels, were not adequately adjusted for in the original studies are limitations of the meta-analysis, the researchers say.

Major Public Health Impact
Jennifer J. Majersik, MD, MS, from the University of Utah in Salt Lake City and a member of the American Academy of Neurology, comments on the study in a corresponding editorial.[3]

“As a stroke neurologist, my patients or their partners regularly ask me whether stress caused their stroke. This is a particularly common question when the stroke occurred in the midst of a difficult life event, or to someone young, working extra hours at school or work. Up to this point, I really have not known how to answer my worried patients,” she writes.

On the basis of this new study, “in answer to my patients’ questions as to whether stress caused their stroke, I will now say ‘maybe’ and then specifically discuss their job type and structure. This is important because there may be ways to reduce job strain, without losing the job,” Dr Majersik says.

“Based on this study,” she added in a statement, “it is reasonable to consider testing interventions aimed at increasing job control, such as decentralization of decision-making and flexibility in job structure, such as telecommuting. If effective, such workplace changes could have a major public health impact.”The authors have disclosed no relevant financial relationships.

STUDY HIGHLIGHTS

Researchers selected prospective cohort studies published before July 20, 2014. Only research on adults with at least 2 years of follow-up was included. Studies that evaluated the risk for stroke only among adults with specific conditions were not considered.

Job strain categories were defined as follows:

High demand, low control: high strain

Low demand, low control: passive

High demand, high control: active

Low demand, high control: low strain

Low-strain jobs were considered the control condition. The main study outcome was the RR for stroke in the other occupational conditions compared with this control condition.

Of 1331 reports in the original search, 6 were included in the meta-analysis. There were a total of 138,782 participants in these 6 studies.

Most participants were middle-aged at the outset of the research, and the mean follow-up period across research was approximately 10 years. There were 4 studies conducted in Europe, 1 in the United States, and 1 in Japan. The overall quality of the included research was good.

High-strain jobs were associated with a significant RR for stroke compared with low-strain jobs (RR, 1.22; 95% CI, 1.01-1.47). However, active or passive occupations were not.

There was no evidence of publication bias in the main result.

The population-attributable risk for stroke associated with high-strain jobs was 4.4%.

3 studies broke out data on job demand and control. High demand and low control failed to independently affect the risk for stroke.

On subgroup analysis, women had a slightly higher RR for stroke associated with high-strain jobs compared with men (RR, 1.33 vs 1.26, respectively).

High-strain jobs increased the risk for ischemic stroke to a slightly higher degree than the risk for hemorrhagic stroke, but this difference was not statistically significant.

CLINICAL IMPLICATIONS

A previous longitudinal study by Kivimäki and colleagues found that high job strain and effort-reward imbalance were associated with a higher risk for cardiovascular mortality, but poor job control was not.

The current meta-analysis by Dingli Xu and colleagues finds that high-strain jobs are associated with a higher risk for stroke, but passive or active jobs are not. Similarly, isolated low control or high demand at the workplace was not associated with a higher risk for stroke.

Implications for the Healthcare Team: Patients may share stories about their lives outside of the clinic or hospital with a variety of different healthcare workers. These stories may include information about high-strain occupations, and the healthcare team should be aware of this condition as a risk factor for stroke and cardiovascular mortality. Information should be shared so that patients can receive the right advice and interventions.